CumulativeSumDistro.lua

--Cumulative Distribution Function
--Author: Xyberviri#5609
--License: GNU GPL v3
--Legal: https://tldrlegal.com/license/gnu-general-public-license-v3-(gpl-3) 
local function GetRandomLoot(loottable)
	local totalweights = 0 --Precompute this value for optimization
	for Pick, Chance in pairs(loottable) do
		totalweights = totalweights + Chance
	end

  local rand = ZombRand(1,totalweights) 
  local weight = 0
  for Pick, Chance in pairs(loottable) do
      weight = weight + (Chance * 10)
      if weight >= rand then
        return Pick
      end
  end
end

--Example:
local PartTable = {
	["none"]                          = 70,
	["ZomboidExtract.ZEZombieBrain"]  = 10,
	["ZomboidExtract.ZEZombieHeart"]  = 10,
	["ZomboidExtract.ZEZombieLung"]   = 10,
	["ZomboidExtract.ZEZombieKidney"] = 10,
	["ZomboidExtract.ZEZombieLiver"]  = 10,
	["ZomboidExtract.ZEZombieBone"]   = 10,
	["ZomboidExtract.ZEZombieFlesh"]  = 10,
  }
  
local item = GetRandomLoot(PartTable)
if item ~= "none" then
	player:getInventory():AddItem(item)
end


--Cumulative Distribution Function (Optimized)
--Author: Xyberviri#5609
--License: GNU GPL v3
--Legal: https://tldrlegal.com/license/gnu-general-public-license-v3-(gpl-3) 
local function GetRandomLoot(loottable,totalweights)
  local rand = ZombRand(1,totalweights) 
  local weight = 0
  for Pick, Chance in pairs(loottable) do
      weight = weight + (Chance * 10)
      if weight >= rand then
        return Pick
      end
  end
end

--Example (Optimized):  
local item = GetRandomLoot(PartTable,140)